Immune mechanisms of Influenza-induced exacerbation of atherosclerosis Influenza A infection is a significant cause of mortality and morbidity worldwide. It is estimated that 3-4 million cases of severe illness and 300,000 deaths due to influenza infection occur annually. During influenza pandemics, the focus is on lung disease, which is the most common cause of death. However, recent epidemiological studies reported significant mortality associated with cardiovascular diseases (CVD) during influenza infection. Atherosclerosis is a common cause of coronary artery disease (CAD), including MI, stroke, and heart failure. The innate and adaptive immune response to modified lipids and vascular endothelial cells causes a series of events that result in plaque formation in medium to large-sized arteries. If inflammatory stimuli continue, plaques become vulnerable to rupture and can cause MI. However, the mechanism involved in the influenza-induced increase in MI incidence is not clear. Our long-term research goal is to understand the impact of lung-vascular interactions in atherosclerosis. The objective of this application is to determine how influenza infection directly or indirectly impacts the outcome of atherosclerosis. In Aim 1, we will characterize myeloid and lymphoid cellular subsets from lung, aorta, and spleen at various time points (early, peak, recovery phase) after fluorescent-labeled (Color-flu) influenza infection to track influenza virus along with the cellular recruitment to the vessel. We will then examine whether antigen presentation is impacted by oxidized LDL (oxLDL) using bone marrow dendritic cells (BMDCs) and T cell re- stimulation in vitro. In Aim 2, we will determine the role of type III IFNs (IFN?) systemically (intraperitoneal) or locally in the lung (oropharyngeal) in influenza-induced exacerbation of atherosclerosis. Further, we will determine the effect of IFN? on foam cell formation in macrophages. Finally, we will determine the effect of conditioned media from influenza or type I (IFN?), type II (IFN?), and type III (IFN?)-treated human bronchial epithelial cells (HBE) on human primary aortic endothelial cells (HAEC) to identify the mechanism involved in the lung-vascular interactions in atherosclerosis. In Aim 3, we will determine the effect of IL-17 neutralization systemically (intraperitoneal) or locally in the lung (oropharyngeal) in influenza induced-exacerbation of atherosclerosis. Further, we will determine the effect of lung epithelial IL-17RC signaling during influenza infection in atherosclerotic Apoe-/- mice. Finally, we will determine the effect of conditioned media from influenza- infected or IL-17-treated human bronchial epithelial cells (HBE) on vascular endothelial cells (HAEC) to identify the mechanism involved in the lung-vascular interactions in atherosclerosis. At the completion of these studies, we expect to have made mechanistic insights into the cellular trafficking, viral trafficking, systemic and local effects of IFNs and IL-17, and pulmonary epithelial IL-17 signaling in influenza-induced exacerbation of atherosclerosis that may help to identify immune-based therapeutic targets.